For background reference is made to the following references:    CISPR 16-1-1, “Specification for Radio Disturbance and Immunity Measuring Apparatus and Methods—Part 1: Radio Disturbance and Immunity Measuring Apparatus” (1999).    S. Hashimoto and H. Misaizu, “Impulse Signal Detector”, JP2000333213.    M. Hirose et al., “Device for Measuring the Average Value of Pulse Signals”, U.S. Pat. No. 5,416,798.    T-S Kim et al., “Partial Discharge Measuring Method using Frequency Spectrum Analyser” KR100206662.    W. Schaefer, “Understanding Impulse bandwidth Specifications of EMI Receivers”, IEEE International Symposium on EMC, pp. 958-961 (1999).    W. Schaefer, “Signal Detection with EMI Receivers”, Conformity, pp. 12-22, July (2002).    W Schaefer, “Measurement of impulsive signals with a spectrum analyzer or EMI receivers”, IEEE Int. Symposium on EMC, Vol. 1, pp. 267-271 (2005).    W. Schaefer, “Narrowband and broadband discrimination with a spectrum analyzer or EMI receiver”, IEEE International Symposium on EMC, Vol. 2, August pp. 249-255 (2006).    W. Skudera Jr., “RF Pulse Detection”, U.S. Pat. No. 5,561,364.    J. B. Taylor and M. K. Ellis, “Method and Apparatus for Distinguishing Narrowband Continuous Wave Signals from Broadband and Impulsive Signals”, U.S. Pat. No. 5,065,334.    Tektronix Inc., “Wide-bandwidth spectrum analysis of transient signals using a real-time spectrum analyser”, CN101300498.